<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .s1{
            font-size: 50px;
            color: red;
        }
        .s2{
            text-decoration: underline;
            color: red;
        }
        .s3{
            text-decoration: underline;
            font-size: 50px;
        }
        .s4{
            text-decoration: underline;
            font-size: 50px;
            color: red;
        }
    </style>
</head>
<body>
    <p class="s1">段落1</p>
    <p class="s2">段落2</p>
    <p class="s3">段落3</p>
    <p class="s4">段落4</p>
</body>
</html>